Ignore userConfig when running checkPot translation comments check

[seanbudd]

Steps to reproduce:

1. Have add-ons installed to a source copy of NVDA
2. Ensure the add-ons contain translator errors, e.g. translatable strings without comments
3. Run scons checkpot
4. Note that uncommented translation strings in userConfig are raised as checkpot errors.

Actual behavior:

Translation string errors are raised for issue with add-ons

Expected behavior:

Including userConfig in the translation comment check should be disabled by default
including userConfig should be an option when running scons checkpot, and disabled by default.

NVDA logs, crash dumps and other attachments:

System configuration

NVDA installed/portable/running from source:

Source